The present invention relates to a system and method for reducing the recovery time required following transitions between write and read modes in a perpendicular recording disk drive system.
A hard disk drive (HDD) preamplifier has two primary modes, read mode and write mode. A critical and challenging specification for an HDD preamplifier is the time required to switch from the write mode to the read mode and to recover the reader output baseline. This write-to-read time is affected by transient signals injected into the preamplifier that come both internal and external sources. The effect of transient signals on the write-to-read time is greatest in perpendicular recording systems. Perpendicular recording systems require the ability to pass very low frequency data, which requires a reduction the preamplifier's low frequency corner from conventional longitudinal system requirements. A reduction in low frequency corner extends the amount of time needed to recover from transients. This increases the sensitivity to transients, which can increase the baseline wander and therefore the write-to-read recovery time. Baseline wander is also undesirable for the read channel data recovery system because it makes it more difficult for the variable gain amplifier (VGA) to track the servo data.
In the past, a great deal of effort has been focused on reducing transient injection from internal and external sources. Other attempts have tried to reduce the transients while still remaining hypersensitive to them. This creates unreasonable requirements on the system that creates the transients and adds risk due to system unknowns. Further improvements in dealing with transients would improve the state of the art.